U.S. counterintelligence chief Bill Evanina said on Wednesday he was skeptical China had followed through on recent promises to curb spying on the United States.

Evanina told a briefing that he had seen "no indication" from the U.S. private sector "that anything has changed" in the extent of Chinese espionage on the United States.

He said 90 percent of private sector and government data systems intrusions are enabled by "spear-phishing," adding that spear-phishing played a role in the massive hack of security clearance data from the U.S. Office of Personnel Management (OPM).

He said, however, he was unaware of any evidence that any parties had so far tried to use personal data hacked from OPM for nefarious purposes. U.S. investigators have privately attributed the OPM hack to Chinese government operatives.

Evanina's comments come ahead of planned ministerial-level talks between the United States and China on Dec. 1-2 to discuss an anti-hacking accord brokered between the two nations in September.

That agreement, reached during Chinese President Xi Jinping's official state visit to Washington, included promises that neither country would knowingly carry out hacking for commercial advantages.

Earlier this week, the G-20 pledged to comply with a similar set of cybersecurity rules barring commercial espionage.

Evanina heads a branch of the U.S. National Intelligence Director's Office called the National Counterintelligence and Security Center, which on Wednesday published a 2016 "National Counterintelligence Strategy" plan.

He said the plan was the first U.S. counterintelligence report to outline measures for dealing with threats and vulnerabilities created by the proliferation of computer databanks and smartphone technology.

Evanina said that over the last two years, the U.S. government has recognized that foreign intelligence services have greatly expanded their efforts to target and collect personal data on Americans, as well as information on the operations of critical U.S. infrastructure, including power and water delivery systems and financial data networks.

He said that when his agency recently polled American companies on their experiences with foreign espionage, 50 percent of the 138 companies which responded said they had already been targeted by foreign spies, and 90 percent of those espionage attempts involved China.